Power transmission



- Mach-24, 1942.

F.y T. HARRINGTON POWER TRANSMISSION Filed June 5, 1938 ATTORNEY Patented Mar. 24, 1942 UNITED STATES PATENT OFFICE 2,277,640 POWER TRANSMISSION Ferris T. Harrington, Detroit, Mich., assig'nor to Vickers Incorporated, ration of Michigan Detroit,

Mich., a corpo- Application June 3, 1938, Serial No. 211,623

2 Claims.

of a combination valve 2I. This valve consists of an unloading valve 22, a check valve 24, and

a relief valve 26.

The valve 22 which is spring biased downwardly has a piston 23. vThe purpose of this valve is to unload the full delivery of pump Ill at a other as a uid motor.

This invention is particularly concerned with a certain predetermined time as will later be depower transmission system adapted for operating scribed more fully. a plurality of hydraulic motors in predetermined The relief valve 26, while shown as similar to sequence and may be used, for example', in a hythat in the Patent No. 2.043.453 t0 Harry F- draulically operate injection molding machine. 1o Vickers, may be of any conventional construction. In the art of injection molding machines, it is The check valve 24 is located in a passage 25 common to provide means for opening and closand permits free ilow of iluid from valve 22 to ing the dies in which the material is molded and valve 26. ram means for injecting the material into the The combination valve also has a tank port 28 mold. and a delivery port 30. The valves 22 and 26 are- Itis essential to inject the hot plastic material adapted to pass fluid from the port 28 through into the die as rapidly as possible to prevent a conduit 29to the tank. premature cooling of the material before the Pump II delivers liuid through a conduit 34 to cavity of the die is completely filled, thus causing the passage 25 connecting unloading valve 22 imperfections in finished Work. The object of and relief valve 26. Port 30 is connected by a this invention is to accomplish this end with a conduit 38 to a check valve 39 and a port 40 of a minimum power input and the: least possible Solenoid-operated four-way valve 42. The latter power. loss resulting in the least heating of the also has cylinder ports 44, 46, and tank ports 48. iiuid medium in the system. It is desirable-"that e. Port 44 is connected by a conduit 50 to the head the pump delivery be maintained at a maximum end of a cylinder 52, and port'46 is connected by during the entire injection cycle to insure maxi-v a conduit 54 to the rod end of cylinder 52. Ports mum speed of the piston. On the other hand, 48 are connected to tank by a conduit 60. during the remaining vparts of the cycle it is de- Conduit 38 has a branch conduit 62 leading to sirable to reduce the pump 'delivery to a minia pressure reducing valve 64 which permits inmum as quickly as possible after the operating dependent adjustment of the injection pressure. pressure rises at the end of a working stroke. A spring 63 of valve 64 holds a valve member 65 Another object of this invention is to provide in its open position as shown in thev drawing. If pump means which will at once deliver fluid at the pressure in a conduit 66 rises above the setlarge volume-low pressure and low volume-high ting 0f Spring 63, Valve member 55 Will mOVe to pressure and pressure responsive means whereby the right, thereby reducing the delivery of fluid the large volume-low pressure delivery may be to the injection cylinder t the predetermined unloaded while the low volume-high pressure depressure. Valve 64 is connected by the conduit 66 livery is utilized for operation of the iiuid motor. to a port 61 of a solenoid-operated four-way Another object is to provide means for effecting valve 68. The latter has cylinder ports lll, "I2 the operation of the aforementioned pressure re'- 40 and tank ports 14. Port 'I2 is connected by a conspcnsive unloading means. duit 'I6 to the head end of a cylinder 18. Port 'IU Still another object is to provide a method for is connected by a conduit 80 to the rod end of the rendering the said unloading means inoperative cylinder 18. Ports 'I4 of the four-way Valve 63 during one portion of the cycle of the uid motor. are connected t0 tank by the cndut 50- In the drawing: 45 Conduit I6 is connected by a conduit 82 to a The single figure is a diagrammatic View of the solenoid-operated three-way valve 84. A movhydraulic and electric circuit of a preferred form able valve member 85 in valve 84 is normally of the present invention. spring biased downwardly which permits free In the drawing, a double pump I0 and II, which flow from the conduit 82 to a conduit 86; at the may be of the fixed displacement type continusame time valve member 85 blocks a tank conduit `ously driven by a prime mover such as an electric 90. The conduit 86 extends to a' chamber 86 of motor I2, has a suction conduit I4 adapted to the unloading valve 22 and the conduit 96 exdraw fluid from a tank I6. Fluid is delivered tends to the conduit 60 to tank. When the mem- "from pump I0 through a conduit I8 to a port 20 ber 85 is raised it blocks the conduit 82 and opens conduit 86 to conduit 90.

by a conduit 96 and the conduit 60. Slidably mounted in cylinder 52 'is a piston 98 which is utilized to press a die |00 against a mold block |02 kthrough a toggle mechanism |04. The

. die |08 carries a. cam4 |06 which when in its extreme left hand position depresses the spool oi the valve 92.

A piston |08, slidably mounted in the cylinder 18, carries a ram Ill) which has for its purpose the injecting of the material to be molded into a mold cavity ||2 of theA mold block |02.

The material for injection is fed from a. hopper ||4 into a chamber ||5.. A heating element ||6 is provided for melting the material'beforeinjection into the mold.

A push button starting switch I8 vis connected to one side of a line L1 and by a conductor |20 to a solenoid |22 of the four-way valve 42, and thence to the other side ofthe line L1.

Piston 98 carries a rod |24 on which is mounted a cam |26 for actuation of single circuit limit switches |28 and |30.v Piston |08 carries aurod |32 having a cam |34 for actuating a single circuit limit switch |36 and a snap switch |38. Snap switch |38 connects the line L1 by a conductor |40 to the operating coil of a single circuit time delay relay |42. 'I'he latter connects the line L1 by a conductor 44 to a solenoid |46 of the three-way valve 84, thence to line L. v

Limit switch |36 connects line L1 to the operating coil of a holding relay |48 by a conductor |31.' The upper circuit of the relay |48 connects the relays operating coil by a conductor |50 and the limitV switch |28 to the line L1, thus forming a holding circuit for relay |48.

Thecenter circuit of the relay |48 extends from line L1 by a conductor |52 and collector ring |53 to a constantly rotating electromagnetic clutch |54, thence by collector ring |55 to line L2. The clutch is driven from a constant speed shaft to form a time delay mechanism |56. The time delay mechanism |56 has a cam disk |51 and is rotatable in a counterclockwise direction by clutch |54 but is held from possible clockwise rotation by a stationary pin |58.l A spring |59 urges the disk |51 clockwise but may be overcome bythe force applied through clutch |54 when energized. When the clutch |54 is released after having rotated the disk |51 counterclockwise, the disk is returned to the position shown in the drawing by spring |59 the inner end of which is f fastened to a shaft |60 which carries disk |51 and the outer end of which is 4fastened to the pin |58. The cam disk |51 carries adjustable cams 6| and |62 which are adapted to depress limit switches |63 and |64 respectively after adjustable predetermined amounts oi rotation oi disk |51.

The lower circuit of relay |48 is included i`n a circuit extending from the line L1, through the limit switch |30, and conductor |66 to the upper'circuit of the limit switch |63 and 4from there by a conductor |68 to a solenoid |10 of the fourway valve 68, and thence to line L2.

The lower circuit of limit switch |63 extends from the line L1 by a conductor |69 to a solenoid |1| of the four-way valve 68, thence to line` L1.

The circuit of limit switch |64 extends from the line L1 by a conductor |12 to a solenoid |14 of the four-way valve 42, thence to line L1.

In operation, starting with the parts in the po- The combined flow of pumps |0 and passes through reliei valve 26, port 30 to conduit 38,

check valve 39, port 40 of the four-way valve 42,

port 46, and the conduit 54, to the rod end of cylinder 52.

As piston 98 is now in its extreme left position, it will not move. The die block |00 also being in its extreme left position causes cam |06 to open'valve 92. Therefore, pressure fluid is passed from conduit 54 through conduit 94, valve 92, conduit 96, and conduit 60 to tank.

Pressure iluid is also delivered from conduit 38, conduit 62, the pressure reducing valve 64, conduit 66, to port 81 of four-way valve 68, port 10, and the conduit 80, to the rod end of cylinder 18. The piston |08 being in its extreme right position, it will not move.

To start the machine, the push button switch the right hand solenoid |22 o! the four-way valve 42 from line L1, conductor |20. Accordingly the valve 42 is shifted to the right.

Pressure fluid from the port 40 is now delivered to port 44 through conduit 50 to the head end of the cylinder 52. lAt the same time port 46 is connected to one of the ports 48. Fluid from the rod end of cylinder 52 therefore passes through conduit 54, ports 46 and 48 of valve 42, and conduit 60 to tank.

As the piston 98 moves to the right to position the die |00 against the mold block |02 through toggle mechanism |04, cam |06 rides oi of bypass valve 92, thereby closing the same. When the piston 98 reaches its extreme right hand position, cam |26 depresses limit switch |30, thereby making the circuit from the line L1, conductor |66 which is closed at relay |48, limit switch |63, conductor |68 to energize the left hand solenoid |10 of the four-way valve 68. Accordingly the valve 68 is shifted to the left. During the small exceeds the spring setting of valve 22, its action on the bottom of piston 23 causes valve 22 to rise, unloading the total delivery of the pump I0 to tank through port 28 and conduit 29.

Pressure nuid from the port 61 is now delivered to the port 12 through conduit 16 to the head end of cylinder 18. At the same time port 10 is connected to one of the ports 14. Fluid in the rod end of cylinder 18 therefore passes through conduit 80, ports 10 and 14 of the four-way valve 68, and conduit 60 to tank. f While pressure fluid is being delivered to the head end of cylinder 16, an equal pressure is being transmitted to the chamber 88 oi unloading valve 22 from conduit 16, conduit 82, three-way valve 84, and conduit 86, thereby preventing the valve 22 from unloading the delivery of the pump I0 to tank. Thus the full delivery of the pump I0 is utilized during the injection stroke of the piston |08 to cause said injection to occur at full speed.

The material, having been fed by hopper ||4 into chamber ||5, is now melted by the heating element ||6. As the piston |08 moves to the left,

its circuit from the line L1 to energize the solenoid |46 through the-conductor |44. Accordingly valve 84 rises, relieving the pressure in the chamber 88 through conduit 86, valve 84, conduit 90, conduit 60 to tank, and at the same time blocking the conduit 82. This permits valve 22 to open, unloading pump while pump continues to deliver oil to cylinder 18 for`the maintenance of pressure thereon, the excess oil ,discharging to tank through relief valve 26.

Just before the piston |08 reaches its extreme left hand position, cam |34 depresses limit switch |36 which establishes a circuit from the line L1, conductor |31 to energize the operating coil of the relay |48. The relay |48 establishes its own holding circuit from line L1, limit switch |28, which is now closed, conductor |50, relay q| 48 to the latters operating coil. At the same time solenoid |10 is deenergized.

The center circuit of relay |48 is now established from line L1, conductor |52 to the electromagnetic clutch |54. When the electromagnetic clutch |54 becomes energized, it clutches time delay mechanism |56, rotating cam disk |51 through shaft |60. After a predetermined interval cam |6I depresses limit switch |63 which establishes a circuit from the line L1, conductor |69 to energize the right hand solenoid |1| of the four-way valve 68. Accordingly valve 68 is shifted to the right. Fluid pressure is then delivered from the pressure port 61 of the valve 68 to port 10,` conduit 80, to the rod end of the cylinder 18, causing'piston |08 and ram ||0 to return from the injection stroke after having dwelled for a period of time equal to the time required for cam |6| to travel from its rest position to where it depresses limit switch |63. Fluid from the head end of the cylinder 18 is returned to tank by conduit 16, ports 12 and 14 of the four-way valve 68, and conduit 60.

Cam |34 now rides off of limit switch |36, but relay |48 remains energized because of its own holding circuit. Cam |34 also contacts snap switch |38, breaking the circuit to the time delay relay |42, causing it to deenergize which in turn breaks the circuit to the solenoid |46 of valve 84. The spool of valve 84 is now spring biased downwardly opening chamber 88 to tank pressure through conduit 86, valve 84, and conduit 82.

Cam disk |51 continues to revolve; until after a predetermined time, cam |62 depresses limit switch |64 establishing a. circuit from the line L1, conductor |12 to energize the left hand solenoid |14 of the four-way valve 42. Accordingly valve 42 is shifted to the left, delivering pressure fluid from the pressure port 40 of valve 42 t0 port 46, conduit 54 to the rod end of the cylinder 52, causing the piston to retract after having held die against mold block |02 for a predetermined period of time to allow the injected material to cool in the mold ||2, this period being equal to the time taken by cam |62 to depress limit switch |64 after cam |6| has depressed limit switch |63. Fluid from the head end of cylinder of the ports 48 of the valve 42,and conduit 60.

When cam |26 depresses limit switch |28, it breaks the holding circuit |50 of relay |48 which in turn breaks the circuit |52 to the electromagnetic clutch |54 causing it to release time delay mechanism |56. Accordingly cam disk |51 is re- 1 turned to the position shown in the drawing by 52 is returned to tank by conduit 50, port 44, one 75 the action of the spring |58, and solenoids |14 and |1| are thereby deenergized.

As the die |00 reaches its extreme left hand position, cam |06 depresses valve 82, bypassing the pressure fluid from conduit 54, through conduit 84, valve 82, conduit 86, and conduit 60 to tank. All of the solenoids being deenergized and the pump delivery being unloaded to tank, the machine now comes to a complete stop. By depressing the push button starting switch ||8, another cycle will take place.

It will be noted that the mechanism above described is peculiarly adapted to meet the peculiar problems arising in an injection molding ma-A chine. The injector ram ||0 must be moved at full speed throughout its entire stroke, and yet at the same time it is necessary to independently vary the pressure which is exerted on this ram. The provision of the control mechanism associated with conduit 86 and chamber 88 permits this maintenance of full speed at the piston |08 without causing wastage of power during the other three strokes of the operating cycle when the piston 88 or |08 stalls at the end of such stroke.

It will be noted that the inner limit of stroke of the injector ram ||0 may vary due to differences in density, softness, or ash leakage of the material injected, and for this reason the switch |38 is arranged to be actuated at a point somewhat prior to the end of the shortest injecting stroke which is ever encountered, and the time delay relay |42 is utilized for controlling the three-way valve 84. 'Ihus it is made certain that the pump |0 will not be unloaded before the completion of an injecting stroke regardless of variations in length thereof, while at the same time it is insured that pump |0 will be unloaded in a reasonably short interval after the completion of this stroke.

The reducing valve 64 pro'vides for independent adjustment of the pressure effective during the injection stroke in such a. manner that this pressure may be adjusted without disturbing the maximum pressure settings of the relief valve 26 or the unloading valve 22.

'I'he check valve 38 assists in maintaining the die block |00 closed and prevents any momentary pressure drops which might occur in the line 62 as the injection stroke starts from ailecting the piston 88. l

While the form of embodiment of the invention, as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows:

1. A uid power transmission system comprising a plurality of uid motors, a large volume pump and a small volume pump, directional control means and conduits including a common delivery conduit connecting said pumps to deliver uid jointly to each of said motors in sequence, an unloading valve responsive to the delivery pressure in said common delivery conduit for bypassing the delivery of the large volume pump when the pressure in said commondelivery conduit exceeds a predetermined value, and Valve means controlled by one motor for temporarily rendering the unloading valve ineffective during at least a portion of the working stroke of said one motor.

2. A iiuid power transmission system comprising two pump-means forming a common source of pressure uid having a common delivery conduit, a uid motor operable on the fluid from said source in predetermined cycles, means for controlling the delivery of iiuid to the motor, means for bypassing the delivery of one pump in response to predetermined pressure rise in the delivery conduit, said means including a member shiftable between a rst and second position for 4 amano y l controlling the pump bypass to cause delivery respectively of a large or a small volume, means biasing the member toward the iirst position, first piston means effective to shift and maintain said member in the first position, second piston means effective to shift said member to the second position, a conduit permanently connecting `the second piston means with the delivery conduit, and a conduit and valve selectively connecting the iirst piston means to one side of the motor or to an exhaust.

FERRIS T. HARRINGTON. 

